1. Field of the Invention
Aspects of the present invention relate to a thin film transistor (TFT), a method of fabricating the TFT, and a display device including the TFT, and more particularly, to a TFT in which a length L (μm) of a channel region of a semiconductor layer and a leakage current Ioff/W(A/mm) per 1 mm of a width W of the channel region of the semiconductor layer satisfies a function Ioff/W=3.4E-15 L2+2.4E-12 L+c, wherein “c” is a constant ranging from 2.5E-13 to 6.8E-13, a method of fabricating the TFT, and a display device including the TFT.
2. Description of the Related Art
In general, thin film transistors (TFTs) are used as active devices of active matrix liquid crystal displays (AMLCDs) and switching devices and driving devices of organic light emitting diode (OLED) display devices. It is necessary to control the characteristics of a TFT according to the characteristics of each device. In this case, a leakage current significantly affects the characteristics of the TFT.
Conventionally, in a TFT using a polycrystalline silicon (poly-Si) layer, crystallized using a metal-free crystallization technique, as a semiconductor layer, a leakage current is proportional to the width of a channel region and inversely proportional to the length of the channel region. However, even if the length of the channel region is increased in order to reduce the leakage current, it is difficult to produce the intended effect. Furthermore, in a display device, as the length of a channel region increases, the size of the display device also increases and an aperture ratio decreases. Therefore, there is a specific technical limit to increase the length of the channel region.
Meanwhile, a vast amount of research is being conducted on a crystallization technique using a crystallization-inducing metal, for example a metal induced crystallization (MIC) technique, a metal induced lateral crystallization (MILC) technique and a super grain silicon (SGS) technique because the techniques may crystallize an amorphous silicon (a-Si) layer at a lower temperature in a shorter amount of time than a solid-phase crystallization (SPC) technique or an excimer laser annealing (ELA) technique. However, in a TFT using a poly-Si layer crystallized using the crystallization-inducing metal as a semiconductor layer, a leakage current of the TFT varies irrespective of the length or width of a channel region unlike in typical TFTs.
Therefore, in the TFT using the poly-Si layer crystallized using the crystallization-inducing metal as the semiconductor layer, it is impossible to predict a leakage current relative to the size of the channel region of the semiconductor layer. Also, it is difficult to determine the size of the channel region in order to obtain a desired leakage current.